The large intestine is the site that is typically most inflamed in Crohn’s disease and ulcerative colitis, which are thought to result when the immune system is not able to keep the peace with trillions of resident gut microbes. The immune system does this by recruiting specific cell populations, like regulatory T cells (Tregs), to the gut. Kim et al. now suggest that the orphan G protein–coupled receptor GPR15 is expressed by Tregs and required for Treg homing to the large intestine in mice.